Yazoo Clay

Yazoo Clay is a clay geologic formation in Alabama, Louisiana, and Mississippi. It was named after a bluff along the Yazoo River at Yazoo City, Mississippi.^[1] It contains is a type of clay known as montmorillonite, making it a poor foundation material due to the fact that moisture causes extreme changes in volume. Sand, pyrite, and marl have all been noted in the formation. It preserves fossils from the Eocene, including the prehistoric cetaceans Basilosaurus and Zygorhiza, and the marine snake Pterosphenus.^[1][2] Sharks, rays, eels, and fish have also been found from the formation.^[3]

Yazoo Clay
Type	Formation
Unit of	Jackson Group
Sub-units	North Twistwood Creek Member, Cocoa Sand Member, Pachuta Marl Member, and Shubuta Member
Overlies	Moodys Branch Formation
Lithology
Primary	clay
Other	sand, marl
Location
Region	Alabama,  Louisiana, and  Mississippi
Country	United States
Type section
Named for	Yazoo River

See also

• List of fossiliferous stratigraphic units in Alabama
• List of fossiliferous stratigraphic units in Mississippi
• Paleontology in Alabama
• Paleontology in Mississippi

References

1. Monroe, Watson H. (1954). "Geology of the Jackson Area Mississippi" (PDF). United States Geological Survey Bulletin. 986: 56–62. Retrieved 27 June 2018.
2. Breard, Sylvester Q.; Stringer, Gary L. (1995). "Paleoenvironment of a Diverse Marine Vertebrate Fauna from the Yazoo Clay (Late Eocene) at Copenhagen, Caldwell Parish, Louisiana" (PDF). Gulf Coast Association of Geological Societies Transactions. 45.
3. https://www.mdeq.ms.gov/wp-content/uploads/2017/06/Circular_1.pdf

• Various Contributors to the Paleobiology Database. "Fossilworks: Gateway to the Paleobiology Database". Retrieved 17 December 2021.
• Hosman, R.L. (1996). "Regional Stratigraphy and Subsurface Geology of Cenozoic Deposits, Gulf Coastal Plain, South-Central United States" (PDF). United States Geological Survey Professional Paper. 1416-G: G22.